1. Field of the Invention
The invention relates generally to devices for injecting fuel oil into a boiler or furnace and, more particularly, to devices which mix fuel oil with air or steam to decrease fuel oil droplet size.
2. Background Art
Conventional burners for fuel oil, used in industrial boilers and the like, may be provided with pipes in which fuel oil and steam and/or compressed air are mixed. The pipes terminate in a nozzle having conduits through which the fuel oil is directed radially outwardly, then inwardly through channels, and finally out through openings spaced circularly around a nozzle head. The nozzle effects mixing of the fuel oil with the steam or air and atomizes or reduces the size of the fuel oil droplets.
Decreasing the size of fuel oil droplets is desirable because it creates a more stable flame and the amount of nitrogen oxides (NO.sub.x) (particularly NO and NO.sub.2, both of which are air pollutants) produced when fuel oil is burned increases with increases in fuel oil droplet size. In addition, it is believed that a small droplet size provides for more efficient burning and thus greater heat production than is created during combustion of fuel oil of larger droplet size. While nozzles of conventional fuel oil burners may decrease droplet size, there is still a need for devices that further lower droplet size.
In the past, modification of fuel oil burners has been constrained by the fact that such modifications generally increase the pressure drop across the atomizing element. Increased pressure drop is undesirable because it requires increasing the fuel oil supply pressure in order to achieve the desired atomization and delivery of sufficient amounts of fuel oil.
Therefore, there is a need for a fuel oil atomizer which decreases droplet size while not unacceptably increasing the pressure drop of the fuel oil as it passes through the atomizer.